Electroluminescent solid state device

ABSTRACT

An electroluminescent solid state device includes an active body member that is formed of a single crystalline metal oxide, such as aluminum oxide, that is doped with a rare earth element, such as erbium and/or terbium and an activator atom such as oxygen and/or fluorine. The metal oxide body member is electron excited by kinetic electrons that are emitted by a cold cathode. The ends of the metal oxide body member are polished to form a Fabry-Perot resonator, thus providing for coherent radiation from the device. As an alternative to the use of a Fabry-Perot cavity, an acoustic wave generator is associated with the metal oxide body member in order to launch acoustic waves into the body member. The frequency of energization of the acoustic wave generator operates to select a radiation wavelength from one or more emission wavelengths that are produced by doping the metal oxide body member with one or more rare earth elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electroluminescent solid state devices, andmore particularly, to an electroluminescent solid state device having asingle crystalline metal oxide that is doped with one or more rare earthelements and an oxygen and/or fluorine activator atom.

2. Description of the Related Art

Solid state electroluminescent devices generally include a body of asingle crystalline material that emits electromagnetic radiation when anelectrical bias is placed across the body. The body generally includesmeans for causing the excitation of electrons in order to generate theradiation. Such means can include a PN junction within the body, or ametal insulator n type semiconductor (m-i-n) structure. The wavelengthof the generated radiation is dependent on the composition of thematerial that comprises the body, including any dopants that are in thematerial.

Although early electroluminescent devices consisted of polycrystallinesemiconductors, electroluminescent devices have been made from singlecrystalline semiconductor materials, particularly the group III-Vcompounds, and alloys thereof. It is known that doping a semiconductorwith a rare earth element, such as erbium or terbium, provides a devicethat can generate radiation at a wavelength that is highly suitable foroptical transmission purposes. However, it has been found thatsemiconductor devices that are doped with a rare earth element are notparticularly efficient.

The concept of doping a transparent material with a rare earth elementis known, for example, in U.S. Pat. No. 5,262,365 to Oyobe et al. Thispatent provides a silica-based glass that is doped with a rare earthelement, aluminum, and fluorine. Oyobe seeks to avoid thecrystallization problem that occurs when silica glass is co-doped with arare earth element and aluminum. A SiO₂ host glass is doped with therare earth element erbium, or neodymium, aluminum, and fluorine. Theglass composition of this patent is expressed by a glass matrix of a R₂O₃ Al₂ O₃ SiO₃ system, wherein R represents a rare earth element, andfluorine doping is conducted by substituting the oxygen of the systemwith fluorine.

The use of a doped crystal to form a laser is known. For example, U.S.Pat. No. 5,299,218 to Ban et al describes a blue light laser having thethree embodiments shown in FIGS. 1-2, FIG. 3, and FIG. 4. In FIGS. 1-2,an active layer is activated by electrons that are emitted by tips thatare within a field emission tip array. This array is energized by anelectrostatic field application apparatus. The electrons pass through avacuum space, and then impact the active layer. This active layer may bea doped alkali halide crystal, i.e. NaI doped with Tl (NaI:Tl), LiI:Eu,or CsI:Tl, or the active layer may be an un-doped alkali halide crystal,i.e. NaI, or the active layer may be an anthracene crystal, atrans-stilbene crystal, or the like. In the FIG. 3 embodiment, theactive layer is a fiber that acts as a light waveguide. The remainder ofthe FIG. 3 device is the same as FIGS. 2, 3. This active layer is formedby crystal growth of anthracene. In the FIG. 4 embodiment, the activelayer is an alkali halide doped, or undoped crystal, or an organiccrystal and the remainder of the structure is the same as the FIGS. 1, 2embodiment.

Also of general interest relative to wavelength tuning is U.S. Pat. No.5,425,039 to Hsu et al wherein a tunable, single frequency, fiber opticlaser is provided having an erbium:yttererbium phosphate glass fiber, orerbium:ytterbium phospho-silica glass fiber. A rare earth ion dopedglass fiber is also mentioned. Wavelength tuning is achieved bytemperature variation of laser gain cavity length, or byelectromechanical variation of laser gain cavity length.Electromechanical tuning with a PZT transducer is also mentioned.

While prior devices have been generally useful for their limitedintended purposes, it would be desirable to have an electroluminescentdevice that is doped with a rare earth element to achieve radiation atthe desired wavelength, but which is formed of a material that providesgreater efficiency to the device.

SUMMARY OF THE INVENTION

The present invention is directed to an electroluminescent solid statedevice that includes a single crystalline metal oxide body that is dopedwith one or more rare earth elements, and with oxygen and/or fluorine.Electron activation means are provided for injecting kinetic electronsinto the body in order to generate radiation within the body.

This invention provides an electroluminescent device (10 of FIG. 2)having a body of single crystalline metal oxide (20 of FIG. 2) that isdoped with one or more rare earth elements and with oxygen and/orfluorine, in combination with a means (24 of FIG. 2) for injectingkinetic electrons into the body in order to generate radiation withinthe body.

In one embodiment of the invention, the two opposite ends of theelongated body of single crystalline metal oxide are parallel and aremirror polished to form a Fabry-Perot cavity, and thus provide for thebody's coherent electromagnetic radiation output.

In another embodiment of the invention, an acoustic wave generator (200of FIG. 4) is provided on the body of single crystalline metal oxide inorder to launch acoustic waves that travel back and forth down thelength of the body. In this embodiment, the frequency of energization ofthe acoustic wave generator operates to control the wavelength of thebody's coherent electromagnetic radiation output.

An object of this invention is to provide an excitation means (forexample, a cold cathode excitation means), for impact exciting a singlecrystalline metal oxide body with electrons to thereby generateradiation within the body. The body is arranged to emit the generatedradiation from a surface thereof. The body comprises a Fabry-Perotcavity, or the body is provided with a piezoelectric structure thatsends acoustic waves through the body in a manner to define the emissionwavelength of device.

In an embodiment of the invention, the body comprises single crystallinealuminum oxide that is doped with a rare earth element, such as erbiumand/or terbium and with oxygen and/or fluorine.

The rare earth element is essential to the production ofelectromagnetic, or light emission from the metal oxide body, and theoxygen and/or fluorine atoms attach to the atoms of the rare earthelement(s) and operate to put the rare earth element(s) into a 3+ statethat is needed for emission to occur.

When the doped metal oxide body is impacted with kinetic electrons,energy is provided to one of the remaining electrons of the rare earthelement(s), promoting the rare earth element(s) to a higher energy"excited" state, and emitting the difference energy between the"excited" state and a ground state as radiation.

These and other objects, features and advantages of this invention willbe apparent to those of skill in the art upon reference to the followingdetailed description, which description makes reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a top and side perspective view of a box-shaped solid stateelectroluminescent device in accordance with the invention, this figureincluding a three-dimensional coordinate system wherein the X-directionidentifies the length of the device, the Y-dimension identifies theheight of the device, and the Z-dimension identifies the width of thedevice.

FIG. 2 is a section view taken in a X-Y plane that is identified by adotted line 2 in FIG. 1.

FIG. 3 is a section view taken in a Y-Z plane that is identified by adotted line 3 in FIG. 1, FIGS. 2 and 3 comprising an embodiment of theinvention having a Fabry-Perot cavity.

FIG. 4 is an end view of an elongated electroluminescent body that iscontained within the electroluminescent device of FIG. 1, this viewshowing in greater detail, a metal contact layer or electrode thatcovers the top surface of the electroluminescent body, and this viewalso showing an embodiment of the invention wherein an acoustic wavegenerator in the form of a piezoelectric transducer having a pair ofmetal interdigitated finger electrodes that are provided on the bottomsurface of the electroluminescent body.

FIG. 5 is a top and side perspective view of the piezoelectrictransducer of FIG. 4, this view showing the transducer's pair ofphysically spaced and interdigitated finger electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a top and side perspective view of an elongated box-shapedsolid state electroluminescent device 10 in accordance with theinvention. In FIG. 1, the X-direction identifies the length of device10, the Y-dimension identifies the height of device 10, and theZ-dimension identifies the width of device 10.

While physical size is not a limitation on the spirit and scope of thisinvention, as an example, device 10 may have a length of in the range ofabout 1.0 to 10.0 millimeters, a height in the range of about 1.0 to 5.0millimeters, and a width in the range of about 0.1 to 1.0 millimeters.

Device 10 comprises six generally flat, or planar, walls that define asealed or air-tight box-shaped housing. A top wall 12 comprises anelectrically conductive metal plate. Top wall 12 is generally parallelto a bottom wall 14 that is also formed of an electrically conductivemetal plate. The material from which metal plates 12, 14 are formed isnot critical, and aluminum, gold or nickel can be used.

The two end walls 18, 118 are formed of an electrically insulatingmaterial, preferably they are mutually parallel, and at least one of thetwo walls 18, 118 is transparent to the electromagnetic radiation thatis emitted externally of device 10. Again, the material from which endwalls 18, 118 are formed is not critical to the invention.

The two side walls 16, 116 are also formed of an electrically insulatingmaterial, and preferably are mutually parallel. Each side wall 16, 116includes a generally centrally located, metal, and cylindrical electronfocusing lens 28, 128, each the metal lens 28, 128 being biased by theapplication of a negative-polarity DC voltage (see 52 of FIG. 3). Thematerial from which side walls 16, 16 and lens electrodes 28, 28 areformed are not critical to the invention.

FIGS. 2 and 3 show an embodiment of an electroluminescent solid statedevice 10 wherein an internal radiation generator in the form of a body20 is formed as a Fabry-Perot cavity.

Body 20 is formed of a single crystalline metal oxide that is selectedfrom the group Al₂ O₃ (sapphire), ZnO, MgO, LiNbO₃, TiO₃, SrTiO₃, BaTiO₃and quartz. Single crystalline metal oxide body 20 is doped with one ormore rare earth elements selected from the group erbium, terbium,praseodymium, neodymium, samarium, europium, dysprosium, holmium,thulium and ytterbium, and with an activator atom that is selected fromthe group oxygen and/or fluorine.

Of the above-noted single crystalline metal oxides, sapphire (singlecrystalline aluminum oxide), LiNbO₃, and BaTiO₃ are preferred. Use oferbium as the rare earth element results in infra-red radiation. Use ofterbium as the rare earth element results in green radiation.

For example, single crystalline metal oxide body 20 can be doped withthe rare earth element(s) to a level of about 10¹⁸ to about 10¹⁹ atomsper cubic centimeter, and can be doped with oxygen and/or fluorine to alevel of about 10²⁰ atoms per cubic centimeter.

Device 10 includes an electron excitation means 24 (for example, a coldcathode excitation means 24), for impact exciting single crystallinemetal oxide body 20 with electrons, to thereby generate radiation withinbody 20. Body 20 may be arranged to emit the generated radiation from asurface thereof, or from an edge thereof. In order to form device 10into a laser that emits substantially coherent radiation, body 20 isconstructed as a Fabry-Perot cavity.

It is to be noted that in an embodiment of the invention to be describedrelative to FIGS. 4 and 5, body 20 is provided with an acoustic wavegenerator in the form of a piezoelectric (PZT) transducer 200 that formsa distributed feedback Bragg reflector that defines the radiationwavelength of device 10.

The Fabry-Perot cavity of FIGS. 2 and 3 defines the resonant mode thatis needed to produce lasing action, whereas PZT transducer 200 of FIGS.4 and 5 operates to fine tune the radiation wavelength of the laseroutput. That is, when two or more rare earth elements are used to dopesingle crystalline metal oxide body 20, PZT transducer 200 operates toprovide for the selection of the one of two or more radiation wavelengththat will in fact lase.

An embodiment of a device 10 in accordance with the invention included asapphire electroluminescent body 20. Sapphire body 20 was implanted withEr²⁺ (i.e., double ionized erbium) at 400 kV with a dose of 10¹⁵ ionsper square centimeter, and was implanted with oxygen at 80 kV at a doseof 10¹⁶ ions per square centimeter. Sapphire body 20 was annealed at900-degrees centigrade for one hour in 10 Torr of NH₃. Such a sapphirebody 20 can also be annealed in other gases, such as nitrogen or oxygen,in vacuum or in ambient air.

In one aspect of the invention, an electroluminescent device is providedhaving an Al₂ O₃ single crystalline metal oxide body that is doped witha rare earth element(s) that is selected from the group erbium and/orterbium, having the addition of an element(s) that is selected from thegroup oxygen and/or fluorine, and having electron injection means forinjecting kinetic electrons into the Al₂ O₃ single crystalline metaloxide body in order to generate electroluminescent radiation from theAl₂ O₃ single crystalline metal oxide body.

As seen in FIGS. 2 and 3, an X-direction elongated electroluminescentbody 20 is located on the inner and top surface 22 of metal bottom plate14, one end 120 of body 20 being located adjacent to the inner surfaceof end wall 118. A metal contact layer 23 extends along the top surfaceof body 20. A narrow extension 25 of contact layer 23 extends down oneside of body 20, and along at least a portion of the bottom surface ofbody 20, so as to make electrical contact with the inner and top surface22 of metal bottom plate 14.

An electron excitation means in the form of a cold cathode 24 is locatedon the inner and bottom surface 26 of top metal plate 12. As seen inFIG. 2, cold cathode 24 is generally aligned with electroluminescentbody 20. That is, cold cathode 24 extends over and along most of theX-direction length of electroluminescent body 20. Electron excitationmeans 24 may also comprise a line of field emitters, or a line ofnegative electron affinity material, such as diamond, AlN, or p-type GaNthat is treated with a low work function material, as described in thearticle by J. I. Pankove and H. Schade, APPLIED PHYSICS LETTERS, Vol.25, p 53, 1974.

As seen in FIG. 3, each of the two side walls 16, 116 includes acylindrical electron focusing lens 28, 128. The metal lens 28, 128 aregenerally aligned in the Z-direction, and include two parallel elongatedelectrodes 38, 138 that run along the interior of side walls 16 and 116,parallel to cold cathode 24 and anode electrode 23. The lens system 28,128, 38, 138 operates to optimize the electron current density thatflows between cold cathode 24 and body 20 via its metal anode electrode23. In practice, a positive DC voltage 50 is applied to body 20, anegative DC voltage 51 is applied to cold cathode 24, and a negative DCvoltage 52 is applied to each of the two lens electrodes 28, 128, as isshown in FIG. 2 at 50, 51 and 52, respectively. By way of example only,DC voltages 51 and 52 may be in the range of about 10 to 1000 DCV, whilebody 20 is at ground potential. Alternatively, cold cathode 24 may be atground potential, while body 20 is biased positively by a VC voltage inthe range of about 10 to 1000 volts.

As shown in FIG. 2, in an embodiment of the invention, bottom metalplate 14 included a groove 30 within its inner surface 22 adjacent theend 220 of body 20, and a layer of electrical insulating material 34 wascoated over the inner surface 22 of bottom metal plate 14, around body20, and over groove 30. A getter 32 (for example, a filament of Ti), waslocated within groove 30. Getter 32 was flashed in order to provide forevacuating the FIG. 1 housing that is formed by top and bottom metalplates 12 and 14, electrically insulating side walls 16, 116, andelectrically insulating end walls 18, 118.

In another embodiment, getter 32 and groove 30 were not used. In thealternative, the box-shaped housing of FIG. 1 was closed and sealed in avacuum, thus avoiding the need for getter 32 and simplifying the innersurface shape of bottom wall 14.

In operation of electroluminescent device 10, negative voltage 51 isapplied to cold cathode 24 through top metal wall 12, as positivevoltage 50 is applied to body 20 through bottom metal wall 14. This DCvoltage potential difference causes cold cathode 24 to emit electronsthat are directed toward electroluminescent body 20. Negative DC biasvoltage 52 is applied to the two metal electron focusing lenses 28, 128to optimize the flow of electrons from cold cathode 24 to body 20. Thisflow of electrons impinges on contact layer 23, and then enters body 20where the rare earth doping element(s) within body 20 is excited by thiskinetic electron impact. This results in the generation of radiationwithin and from body 20.

Electrons entering body 20 impact and excite the rare earth element(s),causing the emission of electromagnetic radiation. This radiation isemitted from the end 120 of body 20 that is adjacent to end wall 118. Asa result, electromagnetic radiation exits device 10 through end wall118. Since the ends 120, 220 of body 20 are polished and aresubstantially parallel in FIGS. 2 and 3 to thus form a Fabry-Perotcavity, substantially coherent radiation is emitted from body 20.

In an embodiment of the invention, where erbium is the rare earth dopingelement and where oxygen is also present as an activator, the erbiumatoms are in a 3+ state because the erbium atoms have given up the outerthree electrons to neighboring oxygen atoms. The bombarding electronsthat thereafter originate from cold cathode 24 give their kinetic energyto the remaining electrons within the erbium atoms, thus promoting theerbium atoms to an excited state from which the erbium atoms then returnto the lower ground state, thus emitting as radiation a different energythat is represented by the quantity E_(excited) -E_(ground).

FIGS. 4 and 5 show an embodiment of the invention, wherein apiezoelectric transducer 200 is provided on the bottom surface 250 ofelectroluminescent body 20. Acoustic transducer 200 comprises a bottomlayer 220 of piezoelectric material and two top metal contact layers 230and 240 that are individually connected to the two output terminals of asource of AC voltage 260. PZT layer 220 and contact layers 230, 240 maycomprise a thin film layers.

Metal layers 230, 240 are physically separated, and are physicallypatterned to form a pair of interdigitated finger electrodes 101, 202.The wavelength of the coherent radiation that is emitted from body 20 isselected, or fine tuned, by generating a grating of acoustic waves inthe X-Z plane within body 20. These acoustic waves are generated by thepiezoelectric transducer 200 that is formed on the bottom surface 250 ofbody 20.

The frequency of AC source 260 that is connected to drive or energizetransducer 200 by application of an AC voltage to electrodes 230, 240,is adjusted so that the wavelength of the acoustic waves that aregenerated within body 20 is a sub-harmonic of the optical wavelength ofthe coherent radiation that is to be emitted from body 20.

When body 20 is provided with such an acoustic transducer 200, body 20need not comprise a Fabry-Perot cavity, since the transducer's acousticwaves form a distributed feedback that induces coherence of the emittedradiation. Stated another way, a laser requires a resonant structurethat causes light to bounce back and forth between two properly spacedmirror surfaces 120-220 of body 20. In a Bragg reflector as provided bytransducer 200, the reflection is periodic at each maximum of theacoustic wave.

Transducer layer 220 may be formed of LiNbO₃ or BaTiO₃. The pair ofphysically spaced and interdigitated metal finger electrodes 101, 201that are located adjacent to the bottom side or surface 250 oftransducer 200 operate to launch an acoustic wave within body 20 byvirtue of physical deformation of PZT layer 220. As shown by dotted line300, the pattern of interdigitated fingers 101, 201 is preferablyrepeated down the entire X-direction length of body 20 between its twoends 120, 220.

In operation, transducer 200 generates sound, or acoustic waves, thattravel in opposite directions along the X-direction length of body 20.The sum of these opposite direction sound waves forms a stationary, orfixed, position grating. The size and X-direction spacing of fingers101, 202 is such that the acoustic waves generated by transducer 200,and the optical waves generated within body 20 must be in phase, onebeing the harmonic of the other.

Thus, there is provided by the present invention an electroluminescentsolid state device 10 that includes a single crystalline metal oxideelectroluminescent body 20 body that is doped with both a rare earthelement and an activator atom. The activator atom within the metal oxidebody raises the ionization of the rare earth element to +3, so that whenthe rare earth element is impacted by electrons, the rare earth elementcauses the generation of, and the emission of, electromagneticradiation.

Body 20 is only slightly temperature sensitive in that there is only asmall drop in radiation emission over a wide range of temperatures. Body20 provides radiation at several wavelengths when more than one rareearth element is present therein. Body 20 may be tuned, using transducer200 of FIGS. 4 and 5, to cause only a desired one of several wavelengthsto be emitted as coherent radiation.

As described above, erbium and oxygen are implanted into a metal oxidebody, such as sapphire, and the body is then annealed. The erbium/oxygendoping can be achieved by the well-known technique of ion beamimplanting, or these materials can be included in the melt when thesingle crystalline metal oxide material is grown.

While the bombarding of the sapphire body with a massive ion may causebond breaking and disorder within the sapphire body, annealing allowsbond reconstruction and repair of the crystal structure. The implanteddoping material may reside in an interstitial site within the singlecrystal (i.e., in an open space between bonded atoms in the crystal,this space being many times larger than a rare earth atom), in whichcase, the crystal remains unstressed. On the other hand, the dopingmaterial may substitute for an aluminum atom or an oxygen atom, thuscausing a local deformation of the crystal lattice and local stress.

However, in the case where rare earth ions are used as doping materials,the local stresses do not suppress the luminescent properties of therare earth ion. The reasons for this indifference of the host crystal isthat luminescence occurs between states belonging to the inner coreelectrons of the rare earth ion. These electrons belong to the rareearth ion and remain so localized that they do not sense the presence ofadjacent crystal atoms.

Therefore, in either the interstitial or the substitutional case, theluminescent behavior of the rare earth is not strongly affected bycrystal disorder. In fact, rare earth doped glass fibers are notcrystalline, and they are structurally highly disordered and yet theyare used for laser amplifiers.

While this invention has been described in detail while making referenceto preferred embodiments thereof, it is known that others skilled inthat art will, upon learning of this invention, readily visualize yetother embodiments that are within the spirit and scope of thisinvention. Therefore, it is not intended that the above detaileddescription be taken as a limitation on this invention.

What is claimed is:
 1. A solid state electroluminescent lasercomprising:an elongated, single crystalline, metal oxide body selectedfrom the group Al₂ O₃ (sapphire), ZnO, MgO, LiNbO₃, TiO₃, SrTiO₃, BaTiO₃and quartz that is doped with one or more rare earth elements selectedfrom the group erbium, terbium, praseodymium, neodymium, samarium,europium, dysprosium, holmium, thulium and ytterbium and with a rareearth ionizing element selected from the group oxygen and fluorine, saidrare earth ionizing element atom operating to ionize said one or morerare earth elements:an elongated electron emitter spaced from andaligned with said elongated single crystalline metal oxide body; kineticelectrons emitted from said electron emitter operating to impact saidone or more rare earth elements and to raise the energy of electrons ofsaid one or more rare earth elements to an excited state above a groundstate, such that upon return of said one or more rare earth elements tosaid ground state, radiation is emitted by said one or more rare earthelements; and means operable to render said emitted radiation coherent.2. The solid state electroluminescent laser of claim 1 wherein saidmeans operable to render said emitted radiation coherent is aFabry-Perot cavity that includes said elongated, single crystalline,metal oxide body.
 3. The solid state electroluminescent laser of claim 1wherein said means operable to render said emitted radiation coherent isan acoustic generator that is associated with said elongated, singlecrystalline, metal oxide body in a manner to produce a standing wavewithin said elongated, single crystalline, metal oxide body.
 4. Thesolid state electroluminescent laser of claim 3 wherein said standingwave is a sub-harmonic of the wavelength of said coherent radiation. 5.The solid state electroluminescent laser of claim 1 including:electronflow focusing means associated with said elongated, single crystalline,metal oxide body and said elongated electron emitter in a manner tofocus a flow of electrons from said elongated electron emitter to saidelongated, single crystalline, metal oxide body.
 6. The solid stateelectroluminescent laser of claim 5 wherein said means operable torender said emitted radiation coherent is a Fabry-Perot cavity thatincludes said elongated, single crystalline, metal oxide body.
 7. Thesolid state electroluminescent laser of claim 5 wherein said meansoperable to render said emitted radiation coherent is an acousticgenerator that is associated with said elongated, single crystalline,metal oxide body in a manner to produce a standing wave within saidelongated, single crystalline, metal oxide body.
 8. The solid stateelectroluminescent laser of claim 7 wherein said standing wave is asub-harmonic of said coherent radiation.
 9. A solid stateelectroluminescent laser comprising:an elongated, single crystalline,metal oxide body selected from the group Al₂ O₃ (sapphire), LiNbO₃ andSrTiO₃ that is doped with one or more rare earth elements erbium andterbium, and with a rare earth ionizing element selected from the groupoxygen and fluorine, said rare earth ionizing element operating toionize said one or more rare earth elements; an elongated electronemitter spaced from said elongated single crystalline metal oxide body;kinetic electrons emitted from said electron emitter operating to impactsaid one or more rare earth elements, and to raise the energy ofelectrons of said one or more rare earth elements, such that upon areturn of the ionization level of said one or more rare earth elements,radiation is emitted by said one or more rare earth elements; and meansoperable to render said emitted radiation coherent.
 10. The solid stateelectroluminescent laser of claim 9 wherein said means operable torender said emitted radiation coherent is a Fabry-Perot cavity thatincludes said elongated single crystalline metal oxide body.
 11. Thesolid state electroluminescent laser of claim 9 wherein said meansoperable to render said emitted radiation coherent is an acousticgenerator that is associated with said elongated single crystallinemetal oxide body in a manner to produce acoustic and optical standingwaves within said elongated single crystalline metal oxide body.
 12. Thesolid state electroluminescent laser of claim 11 wherein said standingwave is a sub-harmonic of the wavelength of said coherent radiation. 13.The solid state electroluminescent laser of claim 9 including:electronflow focusing means associated with said elongated single crystallinemetal oxide body and said elongated electron emitter in a manner tofocus a flow of electrons from said elongated electron emitter to saidelongated single crystalline metal oxide body.
 14. The solid stateelectroluminescent laser of claim 13 wherein said means operable torender said emitted radiation coherent comprises said elongated singlecrystalline metal oxide body operating as a Fabry-Perot cavity.
 15. Thesolid state electroluminescent laser of claim 13 wherein said meansoperable to render said emitted radiation coherent is an acousticgenerator that is associated with said elongated single crystallinemetal oxide body in a manner to produce a standing wave within saidelongated single crystalline metal oxide body.
 16. The solid stateelectroluminescent laser of claim 15 wherein said standing wave is asub-harmonic of said coherent radiation.
 17. The solid stateelectroluminescent laser of claim 9:wherein said an elongated singlecrystalline metal oxide body is Al₂ O₃ (sapphire) that is doped witherbium; and wherein said coherent radiation is infra-red radiation atabout 1.5 micrometers.
 18. The solid state electroluminescent laser ofclaim 9:wherein said elongated single crystalline metal oxide body isAl₂ O₃ (sapphire) that is doped with terbium; and wherein said coherentradiation is green light.
 19. An electroluminescent device comprising:aclosed housing having a top metal wall, a bottom metal wall, a pair ofinsulating end walls, at least one of which is transparent, and a pairof insulating side walls; an elongated, single crystalline, metal oxidebody selected from the group Al₂ O₃ (sapphire), ZnO, MgO, LiNbO₃, TiO₃,SrTiO₃, BaTiO₃ and quartz that is doped with one or more rare earthelements selected from the group erbium, terbium, praseodymium,neodymium, samarium, europium, dysprosium, holmium, thulium andytterbium and with a rare earth ionizing element selected from the groupoxygen and fluorine, said rare earth ionizing element atom operating toionize said one or more rare earth element; said single crystallinemetal oxide body being mounted on an interior surface of said bottommetal wall; an elongated electron emitter mounted on an interior surfaceof said top wall so as to be spaced from and aligned with said singlecrystalline metal oxide body; first power supply means for applying anegative potential to said electron emitter relative to said singlecrystalline metal oxide body to thereby cause electrons to be emittedfrom said electron emitter and to flow to said single crystalline metaloxide body, said emitted electrons operating to impact said one or morerare earth elements and to raise the energy of electrons of said one ormore rare earth elements to an excited state above a ground state, suchthat upon return of said one or more rare earth elements to said groundstate, radiation is emitted by said one or more rare earth elements andout of said at least one end wall of said housing; means associated withsaid single crystalline metal oxide body operable to render said emittedradiation coherent; electrostatic focusing means mounted in said sidewalls; and second power supply means operating to apply a negativepotential to said electron flow focusing means to thereby focus a flowof electrons from said electron emitter to said single crystalline metaloxide body.
 20. The electroluminescent device of claim 19 wherein saidmeans operable to render said emitted radiation coherent comprises saidsingle crystalline metal oxide body operating as a Fabry-Perot cavity.21. The electroluminescent device of claim 19 wherein said meansoperable to render said emitted radiation coherent comprises an acousticgenerator that is associated with said single crystalline metal oxidebody in a manner to produce an acoustic standing wave within said singlecrystalline metal oxide body.
 22. The electroluminescent device of claim21 wherein said acoustic standing wave is a sub-harmonic of thewavelength of said coherent radiation.
 23. The electroluminescent deviceof claim 22 wherein said closed housing contains a vacuum.
 24. Anelectroluminescent device comprising:a closed housing having a top metalwall, a bottom metal wall, a pair of insulating end walls, at least oneof which is transparent, and a pair of insulating side walls; anelongated, single crystalline, metal oxide body selected from the groupAl₂ O₃ (sapphire), LiNbO₃ and SrTiO₃ that is doped with one or more ofthe rare earth elements erbium and terbium and with a rare earthionizing element selected from the group oxygen and fluorine, said rareearth ionizing element operating to ionize said one or more rare earthelements; said single crystalline metal oxide body being mounted on aninterior surface of said bottom metal wall; an elongated electronemitter mounted on an interior surface of said top wall so as to bespaced from and aligned with said single crystalline metal oxide body;first power supply means for applying a negative potential to saidelectron emitter relative to said single crystalline metal oxide body tothereby cause electrons to be emitted from said electron emitter and toflow to said single crystalline metal oxide body, said emitted electronsoperating to impact said one or more rare earth elements and to raisethe energy of electrons of said one or more rare earth elements to anexcited state above a ground state, such that upon return of said one ormore rare earth elements to said ground state, radiation is emitted bysaid one or more rare earth elements and out of said at least one endwall of said housing; means associated with said single crystallinemetal oxide body operable to render said emitted radiation coherent;electrostatic electron flow focusing means mounted in said side walls;and second power supply means operating to apply a negative potential tosaid electron flow focusing means to thereby focus a flow of electronsfrom said electron emitter to said single crystalline, metal oxide body.25. The electroluminescent device of claim 24 wherein said meansoperable to render said emitted radiation coherent comprises said singlecrystalline metal oxide body operating as a Fabry-Perot cavity.
 26. Theelectroluminescent device of claim 24 wherein said means operable torender said emitted radiation coherent comprises an acoustic generatorthat is associated with said single crystalline metal oxide body in amanner to produce a standing wave within said single crystalline metaloxide body.
 27. The electroluminescent device of claim 26 wherein saidstanding wave is a sub-harmonic of the wavelength of said coherentradiation.
 28. The electroluminescent device of claim 24:wherein saidsingle crystalline metal oxide body is Al₂ O₃ (sapphire) that is dopedwith erbium; and wherein said coherent radiation coherent is infra-redradiation.
 29. The electroluminescent device of claim 2:wherein saidsingle crystalline metal oxide body is Al₂ O₃ (sapphire) that is dopedwith terbium; and wherein said coherent radiation coherent is greenradiation.